BBM Sustainable Design was featured in architecture magazine Dezeen in June for building the first permanent structure in the U.K. made completely out of trash. Located on the campus of the University of Brighton, the “Waste House” is insulated with layers of trash such as toothbrushes, DVDs and even old floppy disks. Several tons of waste chalk were used to construct some of the interior walls, with denim jeans lining some of them for more insulation.

The point is that just about anything can be re-purposed for some other use, particularly in a survival situation. These four items could come in handy when the SHTF.

1. Garbage Bags

It’s fairly common knowledge among so-called preppers that humans can survive several weeks without food, but only 72 hours or so without water. Large, clear lawn bags could end up saving your life if you know the basics of building a solar still.

Dig a hole shaped like a funnel, and place a cup at the bottom. Cover the hole with a flat plastic bag. Use rocks to hold the bag in place, and then use more rocks to weigh down the plastic in the center so it comes to a point which the cup can collect the condensation. It’s best to put green vegetation in the hole or wet the soil with dirty water, including urine. As the sun shines down on the plastic and heats up the inside of the hole, the water will evaporate and collect on the plastic. As the day goes on, distilled water will accumulate in the cup.

Granted this won’t make a lot of water, but enough for you to survive short-term. You can build several solar stills if you have enough plastic, which can provide a reliable source of water indefinitely.

2.Non-Digital Wrist Watch

Those who plan on heading for the hills may find themselves in such a remote area that everything looks the same no matter where you look. Of course, the sun rises in the east and sets in the west, which can help you figure out which direction to travel. But keep in mind, as summer turns to fall, and then winter, the sun sets more towards the south. From the first day to winter to summer, it gradually moves north—unless you live right on the North or South Pole. You can avoid all this potential confusion by using your old wristwatch as a compass.

The caveats are that your watch must be close to the exact time, and the sun will need to be shining. Lie the watch on the ground and turn the hour hand towards the sun. At sunrise, south is halfway between the hour hand and 12 o’clock clockwise, and halfway between the two counterclockwise in the afternoon, according to the Farmer’s Almanac.

This method is not 100 percent precise but will give you a general idea of direction every morning in a nomadic situation.

3. Tree Stand

Some hunters build permanent tree stands on private property and ultimately get to know the terrain and migratory patterns of animals by observing from above. A custom-built tree stand can act as both a lookout and a shelter in several situations.

A tree stand is especially useful in areas prone to flash flooding. It can serve as a refuge until waters recede. It could also save you from a pack of hungry wolves or even a charging buffalo. But the key is making sure the tree is easy to climb. If the tree lacks natural climbing limbs, use climbing sticks or create your own steps. Take a tree stand safety course to learn the intricacies of a safe climbing apparatuses versus others that will ultimately lead to serious injury or death.

4. Glasses

Most people who wear glasses regularly have a spare pair in case of emergencies. But some prescription glasses can potentially save you from freezing to death if you use them as a fire starter.

Stack up enough tinder—toilet paper, duct tape, dry foliage. Hold the glasses about 12 to 14 inches from the fuel, and continue manipulating the angle until the sun’s rays begin heating and ultimately igniting the tinder. Gently blow on it when it starts smoldering until a flame starts, and toss more tinder and wood on it until a strong fire is going.

One man’s trash is another man’s treasure as the saying goes. The term “garbage” takes on a whole new meaning in survival situations which excludes most of the things previously thought of as such.